Winson | 9947f1e | 2019-08-16 10:20:39 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2019 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package android.content.res.loader; |
| 18 | |
| 19 | import android.annotation.AnyRes; |
| 20 | import android.annotation.NonNull; |
| 21 | import android.annotation.Nullable; |
| 22 | import android.content.res.AssetManager; |
| 23 | import android.content.res.Resources; |
| 24 | import android.content.res.XmlResourceParser; |
| 25 | import android.graphics.drawable.Drawable; |
| 26 | import android.os.ParcelFileDescriptor; |
| 27 | import android.util.TypedValue; |
| 28 | |
| 29 | import java.io.IOException; |
| 30 | import java.io.InputStream; |
| 31 | |
| 32 | /** |
| 33 | * Exposes methods for overriding file-based resource loading from a {@link Resources}. |
| 34 | * |
| 35 | * To be used with {@link Resources#addLoader(ResourceLoader, ResourcesProvider, int)} and related |
| 36 | * methods to override resource loading. |
| 37 | * |
| 38 | * Note that this class doesn't actually contain any resource data. Non-file-based resources are |
| 39 | * loaded directly from the {@link ResourcesProvider}'s .arsc representation. |
| 40 | * |
| 41 | * An instance's methods will only be called if its corresponding {@link ResourcesProvider}'s |
| 42 | * resources table contains an entry for the resource ID being resolved, |
| 43 | * with the exception of the non-cookie variants of {@link AssetManager}'s openAsset and |
| 44 | * openNonAsset. |
| 45 | * |
| 46 | * Those methods search backwards through all {@link ResourceLoader}s and then any paths provided |
| 47 | * by the application or system. |
| 48 | * |
| 49 | * Otherwise, an ARSC that defines R.drawable.some_id must be provided if a {@link ResourceLoader} |
| 50 | * wants to point R.drawable.some_id to a different file on disk. |
| 51 | */ |
| 52 | public interface ResourceLoader { |
| 53 | |
| 54 | /** |
| 55 | * Given the value resolved from the string pool of the {@link ResourcesProvider} passed to |
| 56 | * {@link Resources#addLoader(ResourceLoader, ResourcesProvider, int)}, return a |
| 57 | * {@link Drawable} which should be returned by the parent |
| 58 | * {@link Resources#getDrawable(int, Resources.Theme)}. |
| 59 | * |
| 60 | * @param value the resolved {@link TypedValue} before it has been converted to a Drawable |
| 61 | * object |
| 62 | * @param id the R.drawable ID this resolution is for |
| 63 | * @param density the requested density |
| 64 | * @param theme the {@link Resources.Theme} resolved under |
| 65 | * @return null if resolution should try to find an entry inside the {@link ResourcesProvider}, |
| 66 | * including calling through to {@link #loadAsset(String, int)} or {@link #loadAssetFd(String)} |
| 67 | */ |
| 68 | @Nullable |
| 69 | default Drawable loadDrawable(@NonNull TypedValue value, int id, int density, |
| 70 | @Nullable Resources.Theme theme) { |
| 71 | return null; |
| 72 | } |
| 73 | |
| 74 | /** |
| 75 | * Given the value resolved from the string pool of the {@link ResourcesProvider} passed to |
| 76 | * {@link Resources#addLoader(ResourceLoader, ResourcesProvider, int)}, return an |
| 77 | * {@link XmlResourceParser} which should be returned by the parent |
| 78 | * {@link Resources#getDrawable(int, Resources.Theme)}. |
| 79 | * |
| 80 | * @param path the string that was found in the string pool |
| 81 | * @param id the XML ID this resolution is for, can be R.anim, R.layout, or R.xml |
| 82 | * @return null if resolution should try to find an entry inside the {@link ResourcesProvider}, |
| 83 | * including calling through to {@link #loadAssetFd(String)} (String, int)} |
| 84 | */ |
| 85 | @Nullable |
| 86 | default XmlResourceParser loadXmlResourceParser(@NonNull String path, @AnyRes int id) { |
| 87 | return null; |
| 88 | } |
| 89 | |
| 90 | /** |
| 91 | * Given the value resolved from the string pool of the {@link ResourcesProvider} passed to |
| 92 | * {@link Resources#addLoader(ResourceLoader, ResourcesProvider, int)}, return an |
| 93 | * {@link InputStream} which should be returned when an asset is loaded by {@link AssetManager}. |
| 94 | * Assets will be loaded from a provider's root, with anything in its assets subpath prefixed |
| 95 | * with "assets/". |
| 96 | * |
| 97 | * @param path the asset path to load |
| 98 | * @param accessMode {@link AssetManager} access mode; does not have to be respected |
| 99 | * @return null if resolution should try to find an entry inside the {@link ResourcesProvider} |
| 100 | */ |
| 101 | @Nullable |
| 102 | default InputStream loadAsset(@NonNull String path, int accessMode) throws IOException { |
| 103 | return null; |
| 104 | } |
| 105 | |
| 106 | /** |
| 107 | * {@link ParcelFileDescriptor} variant of {@link #loadAsset(String, int)}. |
| 108 | * |
| 109 | * @param path the asset path to load |
| 110 | * @return null if resolution should try to find an entry inside the {@link ResourcesProvider} |
| 111 | */ |
| 112 | @Nullable |
| 113 | default ParcelFileDescriptor loadAssetFd(@NonNull String path) throws IOException { |
| 114 | return null; |
| 115 | } |
| 116 | } |